[Sprint LG G3] auriculogenesis:
I wanted to post this for people who want to try out MM on the LS990 and have fully working 3G and 4G/LTE data on a Sprint network. I'll explain the exact conditions that I personally went through to get it working.

I CANNOT GUARANTEE THAT THESE STEPS WILL WORK FOR YOU. YOU MAY EXPERIENCE PROBLEMS AS MENTIONED BELOW.​

The flashing and setup:

What I personally did was flash BareCee v2 and then updated the PRL and Profile. Afterwards, I dirty flashed BlackSoulxxx's v30b MM port (see: http://xdaforums.com/lg-g3/development/rom-lge-d855-android-marshmallow-ported-t3285025). I rooted the port with SuperSU 2.52 BETA via TWRP. Once I got to the home screen, I was greeted by a notification that stated that I need to update Google Play services. I updated it. Then I confirmed my appropriate APN settings. I'm on RingPlus, so this was important for me to even get mobile data at all.

The fix:

Once I went through all that, I edited /system/build.prop using Solid Explorer with the following lines:

The following two lines might be disabled in your build.prop. If they are active, ensure it's set properly as listed below. It was disabled on mine, so I did NOT touch them or re-enable them:

If you don't care for having your phone unlocked for Global/GSM use, you can edit the following lines to get the Sprint 3G/LTE, airplane mode, etc. status bar icons and branding (as well as disable the Global/GSM network option):

After you have edited the build.prop, give it a reboot and toggle data/airplane mode in the quick toggle/notification pull-down menu until you get data to finally turn on. Once it switches on, it'll work until your next reboot, I believe. You will need to fiddle with the toggle again once you reboot. This is a bug due to the ports. There's no known fix for this besides dirty flashing over BareCee v2, but I can't really say for certain if everybody will have this fixed just by dirty flashing. Dirty flashing also allows the settings switch and data settings panel to work correctly (sometimes).

From what I can tell, ro.cdma.home.operator.numeric is the key factor for getting 3G data to work properly.

Negative repercussions:

You may have issues with Messaging.app and weather.app NOT working/crashing after launch IF YOU DIRTY FLASH. I'm not sure how to fix this issue other than with a CLEAN FLASH.

Others have expressed issues with google play services not working or force crashing and causing the OS to be unstable. Clean flashing fixes this problem, usually.

Fulmics 3.1 and xpirt was the source of this fix and it was stated that this will be included in the next version of Fulmics 3.X. I personally cannot use Fulmics because it's highly unstable for me. It overheats my phone and there's heavy lag with poor battery life.

Other Notes:

I would like to see somebody clean flash BlackSoulxxx's port or Fulmics 3.1 and try this out. I'm too busy to keep flashing/testing and everything I need is working (I don't bother with the stock Messaging app and weather app works fine for me). Please report back if you do this and let us know what happens. I suspect this is the best possible outcome for avoiding force crashes, but it also may mean that the data may not work properly, even after this fix.

Hope this helps somebody. It took me weeks to resolve this issue.

Thanks to:

blacksoulxxx

xpirt

6th_hokage

jglm4u